When the Bible says, "the heavens declare the glory of God" it means
that the GOSPEL is throughout the world, declaring God's glory.
"And I
saw another angel flying in mid-HEAVEN, having an EVERLASTING GOSPEL to proclaim
to those dwelling on the earth, even TO EVERY NATION and tribe and tongue and
people, saying in a great voice...." (Revelation 14:6)
Of course, this
verse is metaphorical. By angel, John must mean messenger. He must be saying
that the prophets and preachers proclaimed the gospel "TO EVERY
NATION".
Also, Paul in Romans 10 says that Psalm
19 is talking about the UNIVERSAL preaching of the
GOSPEL.
Romans 10:16-18 - "And how may they preach if they are not sent?
... Then faith is of hearing, and hearing through the Word of God. But I say,
Did they not hear? Yes, rather, "INTO ALL THE EARTH THEIR VOICE WENT OUT, and to
the ends of the world their words." LXX-Psa. 18:5; MT-Psa. 19:4
Psalm 19 is saying that the voices of the prophets were heard from
"the heavens" (a metaphor for the 'everywhere') and "into all the earth their
voice went out, and to the ends of the world their words."(v4)
This is NOT my interpretation of Psalm 19. It is the Apostle Paul's !!! See Romans 10:18